1. Field of the Invention
The invention relates to a wind power plant with a rotor and at least one angle-adjustable rotor blade and an electric motor, in particular an asynchronous motor, for the movement of a moveable part of the wind power plant, wherein the wind power plant also has a control device. The moveable part can typically be a nacelle, which should be pointed into the wind by adjusting its azimuth angle, or a rotor blade, which should be adjusted with respect to its blade angle, which is also called the pitch angle. The invention also relates to a method for operating a wind power plant with a rotor and at least one angle-adjustable rotor blade, an electric motor, in particular an asynchronous motor, and with a control device.
2. Description of Related Art
A motor-driven yaw drive of the nacelle for a wind power plant is generally known. For example in the textbook by Erich Hau entitled “Windkraftanlagen” (Wind Power Plants), 4th edition, Springer-Verlag, pages 346 ff. a yaw drive system is also called an azimuth adjustment system. This system serves to automatically align the rotor and the nacelle according to the wind direction. There is an independent assembly in the wind power plant, which forms the transition from the nacelle to the top part of the tower from a constructive point of view. The adjustment device hereby turns the nacelle with the rotor mainly around the longitudinal axis of the tower, i.e. around the azimuth angle. For this, an actuating drive in the form of an electrical motor, which is frequently designed as an asynchronous motor, is provided as well as a gear box and a brake.
During the operation of a wind power plant, in particular in turbulent winds depending on the yaw angle of the rotor, very high forces and thus very high torques, so-called yawing moments or yaw moments, can occur. These very high torques can occur both during a yaw movement of the nacelle and when the nacelle is not moving. During yaw movement of the nacelle, these very high torques can lead to power peaks in the drive motors, which reduce the lifespan of the motors and the gear box associated with the motors and also trigger a motor protection switch, which automatically leads to the shutdown of the wind power plant, since the motor protection switch is generally part of the safety chain of the wind power plant. The restart of the motor in a wind power plant is then relatively time-consuming and leads to relatively high power generation outages of the wind power plant.
Corresponding problems can also occur in the drive motors of the angle adjustment of rotor blades. Circumstances in which the motor protection switch is triggered can also occur here in correspondingly turbulent winds, so that further adjustment of the rotor blade is no longer possible, which can also lead to dangerous situations or to the shutdown of the wind power plant. For this reason, relatively largely dimensioned electric motors are normally used for the blade angle adjustment of the rotor blades or several motors work simultaneously or parallel to perform the adjustment of the rotor blade and also the adjustment of the azimuth angle of the nacelle.
EP 1 362 183 B1 discloses an azimuth drive of a wind power plant, in which a control of the rotor blade adjustment is performed depending on a deviation between the determined wind direction and the recorded azimuth position and depending on the deflection of a tower of the wind power plant from the vertical in a floating wind power plant. A force imbalance between different rotor blades is hereby utilized so that an azimuth drive in the form of an electric motor does not need to be turned on or only needs low power in order to achieve an azimuth movement.
A wind power plant with a nacelle and a rotor and at least one rotor blade adjustable around its longitudinal axis is known from EP 1 882 852 A1, wherein an adjustment device is provided, via which an azimuth alignment of the nacelle or a pitch alignment of the at least one rotor blade can be set in a motor-driven manner, wherein the adjustment device has at least one motor and wherein a controller is provided for the motor, which limits the occurring torque on the motor to a maximum predetermined value. A stronger motor is hereby used, which results in a higher breakdown torque, which would overload the gear box if used without torque limiting. Above a maximum holding torque, a slipping through of the electrical brake, which is used as an operating brake, is tolerated. During the designing of the gear box for maximum torque, a slipping through of the electro brake is already tolerated at low torque values. The torque of the motor is limited through activation with different frequencies.
DE 103 07 929 A1 discloses an arrangement for the rotation of a machine nacelle, in particular for a wind power plant, which has a nacelle mount for the rotatable mounting of the machine nacelle on a tower and at least one drive for the rotation of the machine nacelle with respect to the tower, wherein the drive is arranged on the machine nacelle or on the tower with a fastener. The fastening of the drive has at least one friction surface for the clamping of the drive so that the drive can be moved in the fastening as of a specified mechanical load. An overloading of the drive is hereby avoided. A sensor system is also provided, which registers a movement of the drive in the fastening and in this case sends a signal to the system controller and/or a monitoring center.
A controller for an azimuth drive of a wind power plant, with which the load of the azimuth system is reduced, is known from EP 2 037 119 A1.